1. Field of the Invention
The present invention relates to a surge absorber for absorbing surge noise applied on electronic devices.
2. Discussion of the Background
Japanese Examined Patent Publication No. JP-B-63-57918 discloses a surge absorber having a structure in which a conductive ceramic thin film is formed on the surface of an insulating member having a cylindrical shape, a micro-gap is formed to divide the conductive ceramic thin film in the circumferential direction and a total thereof is hermetically sealed in a cylindrical glass in a state where gas is filled at inside thereof. Further, Japanese Unexamined Utility Model Publication No. JU-A-49-80351 proposes a surge absorber in which electrodes each in a shape of a pinnacle having points sharpened toward micro-gaps are formed on an insulating substrate in a flat plate shape.
FIG. 17 and FIG. 18 show sectional views of conventional surge absorbers.
FIG. 17 shows a surge absorber in a cylindrical shape. Explaining the principle of operating the surge absorber, when surge is applied on a cylindrical surge absorber 40, arc discharge is caused in a micro-gap 41 and an enclosed gas is successively ionized by the discharge to cause corona discharge by which surge is absorbed.
FIG. 18 shows a surge absorber 42 in a flat plate shape and the principle of operation is basically the same as that of the cylindrical surge absorber.
However, according to the cylindrical one of the conventional surge absorbers, lead wires are extended from central portions of the both ends of the cylinder and therefore, there poses a problem where surface mounting or automatic mounting thereof is difficult. Further, the outer shape is cylindrical and therefore, air-tight cover material other than glass is difficult to use.
Further, according to the one in a flat plate shape, front ends in the micro-gaps are sharpened and accordingly, there poses a problem where the front ends are liable to chip off by discharge when surge is applied with the result of a short life.